Induction heating device



Jan. 2s, 11964 E. HD1-:HN l3,119,917

INDUCTION HEATING DEVICE Filed Jan. 4, 1961 /NVE/V TOR EDWARD H. DEHNAllo/'nay United States Patent() 3,119,917 INDUCTEUN HEATING DEVICEEdward H. Dehn, (lil City, la., assigner to United States SteelCorporation, a corporation of New .lersey Filed dan. 4, 1961, Ser. No.80,623 Il Claims. (Cl. 219-10.79)

This invention relates to an improved induction heating device.

Although my invention is not thus limited, the device is particularlyuseful in heat-treating ball valve cages used in oil well pumps, forexample as shown in Neilsen Patent No. 2,294,568. A conventional ballvalve cage includes a plurality of internal longitudinal ribs forguiding the ball closure member, and respective fingers at one end ofeach rib for limiting relative movement of the ball in that direction.Such cages are of small size, commonly having an inside diameter of lessthan 2 inches. Desirably the ribs and fingers `are hardened to resistwear which results from constant movement of the ball, but the remainderof the cage is left unhardened to promote toughness. lt is known toemploy induction heating devices for selectively `heat-hardening theribs and fingers, but previous devices with which I `am familiar heatonly one rib and linger at a time. In structures of such small size, ithas been considered impractical to heat ya plurality of ribs landfingers simultaneously for the reason that intermediate adjacentportions of the structure become overheated and lose toughness.

An object of the present invention is to provide an improved inductionheating device which simultaneously heats a plurality of selectedportions on the interior of a small metal article without overheatingintermediate adjacent portions.

A further object is to provide an improved induction heating devicewhich enables all ribs and lingers of a ball valve cage to be heated forhardening in a single operation without adverse effects on the remainderof the cage structure.

A further object is to provide a device which has the foregoing improvedcharacteristics and is of simple construction readily used in existingmanufacturing processes.

In accomplishing these and other objects of the invention, i haveprovided improved details of structure, a preterred form of which isshown in the accompanying drawing, in which:

FlGURE l is a perspective view, with parts broken away, of my improvedheating device;

FIGURE 2 is a cross section of the device on line II-Il of FIGURE l;

`FIGURE 3 is an enlarged longitudinal sectional view of a ball valvecage of the type with which I can use my hea-ting device; and

FIGURE 4 is a cross section of the cage on line lV-iV of FIGURE 3.

As FIGURES l and 2 show, my induction heating device includes asubstantially cylindrical core lll formed of a non-conductingferromagnetic material. Such miaterials are available commercially, andconsist of tine magnetic particles dispersed in a heat-resistant,electrically insulating binder, commonly plastic. An electricallyconductive stern 12 is iixed to the core and extends upwardly therefrom.At least the upper portion of the stem is tubular, having a bore 13. Anelectrically conductive fitting 1-4 is iixed to the side of the stemabove the core. One end of a continuous length of copper tubing 1S,preferably of square cross section, is joined to the iitting 14, whichalso provides communication between the bores of the tubing and stem.Tubing 15 has a convolution '16 which extends downwardly within 'alongitudinal groove 17 in the circumferential face of the core, forms anenlarged loop `1S at the bottom edge of the core, and thence Miceextends upwardly within groove 17 back to the top of the core. Nexttubing 15 extends across the top of the core to one or more additionalcircumferentially spaced grooves 17a and 171), and it has convolutionswhich lie within these additional grooves with loops -at the bottom,similar to the arrangement illustrated for groove 17. The other end oftubing 15 is connected to a tubular auxiliary stem 19 of electricallyconductive material. insulating inserts 20 separate the two lengths oftubing 15 which make up each. convolution 16, and an insulating sheath2l covers the entire core and tubing to prevent direct shorts. l connectIstems l2 `and 19 to a suitable high frequency A.-C. source and also tosuitable means for circulating water through the stems 'and tubing 15.

The particular induction heating device illustrated is designed for usewith a valve cage constructed as shown in FIGURES 3 and 4. This cage hasthree longitudinal ribs 22, 22a :and 22h spaced 120 apart around itsinner circumference. Respective integral fingers 23 are formed at oneend of each rib. To heat-harden the ribs and ingers, I insert the devicewithin the cage and apply current to the stems 12 and 19 and alsocirculate water therethrough -to prevent overheating the tubing )15 andcore lil. Each convolution 16 overlies `a rib 22, 22a or 22h, and eachloop 13 overlies a linger 23. The nonconducting magnetic core lll actsas an intensifier and is essential to attain eicient heating. Theheating effect is concentrated at the ribs and iingers, which quicklyreach critical temperatures for hardening, while intermediate adjacentportions of `the cage structure are not overheated. Following a briefheating step, I remove the device and quench the cage in any suitableknown medium.

From the foregoing description, it is seen that my invention affords `asimple device for inductively heating a plurality of selected portionsof the interior of a small metal article. The particular valve cageillustrated is only one example of the sort of article with which I canuse the device. For other articles it is only necessary to construct thedevice of a size to lit the article and with the convolutions of thecurrent carrying tubing matching the portions to be heated. Insimultaneously heating all the portions to be hardened, -I `achieve afurther advantage over heating them one at a time in that l do notdestroy the hardening attained on one portion Iwhen heating anotherpoition. I believe l have achieved a surprising and unexpected result inlocally heating selected areas with-in a small confined space withoutencountering canceling effects.

While l have shown and described only a single embodiment of myinvention, it is apparent that modifications may arise. Therefore, I donot wish to be limited to the disclosure set forth but only by the scopeof the appended claims.

I claim:

l. An induction heating device for simultaneously heating a plurality ofselected portions on the interior of a small metal article withoutoverheating intermediate adjacent portions, said device comprising asubstantially cylindrical core of non-conducting ferromagnetic material,a conductor having a plurality of convolutions which extend along thesides of said core, each convolution being circumferentially spaced fromadjacent convolutions to concentrate heating of the article to portionswhich the convolutions overle, insulating material separating portionsof said conductor making up the same convolution and covering said coreand conductor, and means for applying high frequency electric current tosaid conductor.

2. An induction heating device for simultaneously heating a plurality ofselected portions on the interior of a small metal article withoutoverheating intermediate adjacent portions, said device comprising asubstantially cylindrical core of non-conducting ferromagnetic material,

a tubular conductor having a plurality of convolutions which extendalong the sides of said core, each convolution being circumferentiallyspaced from adjacent convolutions to concentrate heating of the articleto portions which the convolutions overlie, insulating materialseparating portions of said conductor making up the same convolution andcovering said core and conductor, means for applying high frequencyelectric current to said conductor, and means for circulating coolingWater through the bore of said conductor.

3. An induction heating device for simultaneously heating a plurality ofselected portions on the interior of a small metal article withoutoverheating intermediate adjacent portions, said device comprising asubstantially cylindrical core of non-conducting ferromagnetic material,an electrically conductive tubular stem fixed to an end of said core, atubular conductor electrically connected at one end to said stem withits bore in communication with the bore of said stem, said conductorhaving a plurality of convolutions which extend in series along thesides iof said core, each convolution being circumferentially spacedfrom adjacent convolutions to concentrate heating of the article toportions Which the convolutions overlie, an electrically conductivetubular auxiliary stem electrically connected to the other end of saidconductor with its bore in communication with the bore of saidconductor, insulating material separating portions of said conductormaking up the same convolution and covering said core and conductor,means for applying high frequency electric current to said stems, andmeans for circulating cooling Water through the bores of said stems andsaid conductor.

4. An induction heating device for simultaneously heating a plurality ofselected portions on the interior of a small metal article Withoutoverheating intermediate adjacent portions, said device comprising asubstantially cylindrical core of non-conducting ferromagnetic materialhaving a plurality of circumferentially spaced longitudinal grooves inits sides, an electrically conductive tubular stem xed to the top ofsaid core, a tubular conductor electrically connected at one end to saidstem with its bore in communication with the bore of said stem, saidconductor having a plurality of convolutions which extend in series,each convolution lying within a different one of said grooves and havingan enlarged loop at the bottom edge of said core, each convolution beingcircumferentially spaced from adjacent convolutions to concentrateheating of the article to portions which the convolutions overlie, anelectrically conductive tubular auxiliary stem electrically connected tothe other end of said conductor with its bore in communication with thebore of said conductor, insulating material separating portions of saidconductor making up the same convolution and covering said core andconductor, means for applying high frequency electric current to saidstems, and means for circulating cooling Water through the bores of saidstems and said conductor.

References Cited in the le of this patent UNlTED STATES PATENTS2,749,423 Bisterfeld June 5, 1956 2,759,085 Van Iperen Aug. 14, 19562,777,041 Dustman Ian. 8, 1957 2,785,263 Van Iperen Mar. 12, 19572,825,788 Loving Mar. 4, 1958 2,828,397 Emerson Mar. 25, 1958 FOREIGNPATENTS 635,421 Great Britain Apr. 12, 1950

1. AN INDUCTION HEATING DEVICE FOR SIMULTANEOUSLY HEATING A PLURALITY OFSELECTED PORTIONS ON THE INTERIOR OF A SMALL METAL ARTICLE WITHOUTOVERHEATING INTERMEDIATE ADJACENT PORTIONS, SAID DEVICE COMPRISING ASUBSTANTIALLY CYLINDRICAL CORE OF NON-CONDUCTING FERROMAGNETIC MATERIAL,A CONDUCTOR HAVING A PLURALITY OF CONVOLUTIONS WHICH EXTEND ALONG THESIDES OF SAID CORE, EACH CONVOLUTION BEING